It is well known in the art that light, particularly ultraviolet light, stability can be imparted to polymers by incorporating therein certain chemical structural entities. Such entities can be admixed with preformed polymer or they can be incorporated into the polymer during the monomer polymerization step, for example, as a moiety of the monomer or as a moiety of the polymerization initiator.
Urethane polymers have been light-stabilized by incorporating into the prepolymer solution 4-amino- or 4-(3-aminopropyl)amino-2,2,6,6-tetramethylpiperidine, as disclosed in German Offenlegungsschrift Nos. 2,642,374 and 2,642,386, or bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate, as disclosed in German Offenlegungsschrift No. 2,820,419.
The effectiveness of 2,2,6,6-tetraalkylpiperidines as ultraviolet light stabilizers also is evident in the art as disclosed in German Offenlegungsschrift No. 2,748,362 and by F. E. Karrer, Makromol. Chem. 181, 595-633 (1980), wherein such disclosures the stabilizer is incorporated into a free radical polymerizable monomer. The stabilizer-containing monomer, for example, 2,2,6,6-tetramethyl-4-piperidyl acrylate can be homopolymerized or copolymerized with appropriate free radical copolymerizable monomers to provide polymers having improved light stability. Similar disclosures of acrylate and methacrylate monomers which contain heterocyclic groups and which are polymerizable to polymers exhibiting light stability are made in U.S. Pat. Nos. 4,210,612 and 4,294,949.
U.S. Pat. No. 4,308,362 discloses copolymers having repeat units of maleic or fumaric acid ester or amide, the ester or amide groups of which include alkylpiperidine moieties. The alkylpiperidine moieties impart light stability to the polymers. The light stabilizing portion of the polymer is characterized by low volatility, good migration stability and good compatibility with the substrate polymer to which the light stability characteristic is to be imparted. Azo and peroxy free radical initiators containing ultraviolet light stabilizing groups and their use in preparing free radical initiated polymers which exhibit ultraviolet light stability are disclosed in U.S. Pat. No. 3,956,269. Numerous types of ultraviolet light stabilizing compounds, incorporated into the free radical initiator, are disclosed, for example, phenyl salicylates, o-hydroxybenzophenones, cyanoacrylates and benzotriazoles.
It is an object of this invention to provide anionic polymerization initiators. Another object is to provide such initiators which have light stabilizing characteristics. Still another object is to provide processes for anionically polymerizing monomers by means of such initiators. A further object is to provide anionically polymerized polymers which exhibit stability towards light. A further object is to provide such light stable polymers which can impart light stability to other polymers admixed therewith. Further objects will become apparent hereinafter.